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BUR <br /> monitor (GEM). The GEM was certified as calibrated to factory specifications by the rental <br /> supplier, EquipCo, prior to the sampling event. <br /> At each probe, a reading of ambient air in the vicinity of the probe being tested was recorded <br /> before soil gas was monitored within the probe. Initially, the GEM was attached to the soil gas <br /> probe, the valve was opened, and the initial soil gas probe pressure was monitored and recorded. <br /> Then the GEM's internal pump was activated to extract soil gas from the probe. Readings for <br /> methane, oxygen, and carbon dioxide were monitored until the readings stabilized. After the <br /> readings were recorded, the internal pump was deactivated and the post-reading soil gas probe <br /> pressure was monitored and recorded. The soil gas probe valve was then closed, and the GEM <br /> was disconnected. The Forward Landfill weigh station was also monitored to assess potential gas <br /> accumulations at the foundations. The landfill gas probe and building locations are shown on <br /> Figure 1. <br /> Results <br /> As shown in Table 1, methane was detected above its lower explosive limit (LEL) in GP-10 at <br /> Forward Landfill during the May 8, 2002 monitoring event. The GEM displayed a stable reading <br /> of 8.0 percent by volume for methane at GP-10. Methane was not detected during monitoring of <br /> GP-9 or the weigh station at Forward Landfill. Oxygen readings in soil gas probes were 13.5 <br /> percent by volume in GP-10 and 20.1 percent by volume in GP-9. Carbon dioxide readings were <br /> 1.6 percent by volume in GP-9 and 2.8 percent by volume in GP-10. The relative pressure of the <br /> probes ranged from -0.1 to 0.0 inches of water indicating that the pressure within the soil gas <br /> probes is at or near equilibrium with atmospheric pressure. <br /> These data are generally consistent with previous soil gas data collected on May 1, 2002 at the <br /> Forward Landfill. Soil gas monitoring will be conducted again during the third quarter of 2002. If <br /> you have any questions, please call me at (916) 786-0320. <br /> Sincerely, <br /> J. tt Seyfried, R.G. <br /> Principal Hydrogeologist <br /> Enclosures: Figure 1, Table 1 <br /> cc: Ross Atkinson, RWQCB <br /> Butch Stefan, Forward Landfill <br /> Lochlin Caffey, Allied Waste Industries <br /> Project File, LFR-Granite Bay <br />